The Foreign Office has changed its travel advice to Britons in Mali, urging all but those with urgent business there to leave.

The new advice follows an attempted coup in the west African country on 21 March and specifically warns those in the capital, Bamako, to be cautious.

In a statement, the Foreign Office said: "We advise against all travel to Mali and you should leave if you have no pressing need to remain."

The Foreign Office said a curfew that had been imposed from 6pm to 6am had now been lifted, but added: "We continue to advise British nationals in Bamako to exercise caution and stay away from crowds and demonstrations when travelling around the city.

"There have been reports of some shops beginning to run low on supplies and of long queues forming outside some banks.

"Given ongoing instability in the country, and now that the airport has reopened, you should leave if you have no pressing need to remain."

Heavily armed separatist rebels entered the northern Mali town of Gao on Saturday as army troops sought to respond with helicopter gunships, according to Reuters.

The attack came a day after rebels seized the town of Kidal which, along with Gao and the city of Timbuktu, is one of the three main regional centres of Mali's north.

The rebels have capitalised on the chaos caused by last week's military coup in Bamako, pushing their campaign for a homeland in the vast desert region of Azawad, a territory larger than France.

"I saw them entering the town itself and putting up their Azawad flags," Reuters reported.

Regular army troops stationed in the town have retaliated, he added. "Helicopters have started to take off."

Earlier, heavy gun fire was heard around the main military camp to the west of Gao, which also serves as the biggest garrison for the north.

Mid-ranking officers behind last week's coup accused the government of giving them inadequate resources to fight the rebels. But the coup has emboldened the rebels to take further ground.

Coup leader Captain Amadou Sanogo on Friday pleaded for foreign help to preserve the territorial integrity of the former French colony, a major gold and cotton producer.

But neighbouring countries have instead given Sanogo until Monday to start handing back power to civilians or have the borders shut.